Chilled-iron roll



Patented May 10, 1927.

UNITED STATES PATENT OFFICE...

HARRY E. WALTERS, OI PITTSBTJ'RGH, PENNSYLVANIA, ASSIGNOB T0 UNITED ENGI- mBING'd'. FOUNDRY COMPANY, OF PITTSBURGH, PENNSYLVANIA, A CORPORA- TION OF PENNSYLVANIA.

GRILLED-IRON ROLL.

Io Drawing.

This application is a continuation in art of my applications, Serial No. 100,715, led April 8, 1926, and September 20, 1926.

The resent invention relates to chilled iron ro .for use in rolling mills, and more particularly to chilled cast iron alloy rolls having unusual strength and toughness and a fine grained hard chill. The roll is made by casting in a chill mold, a charge of high carbon iron containin chromium and molybdenum, and having ow limits of sulphur and phosphorus.

I have found that a small amount of molybdenum, when used in connection with chromium and the low limits of sulphur and phosphorus, roduces a chilled cast iron roll of remarkab y increased strength and having a tough close rained white iron pri mary chill which s ades ofl gradually and without a. distinct line of demarcation into a tou h hard and wear-resisting secondary chill having a grain structure closely aproximating that of the primary chill and having a depth greater t an the sub-struc ture chill of the ordinary chilled roll.

The charge is usually made up ofgug iron and scrap, together with the alloy a dltions, and is melted in a furnace, such as an air furnace, in which the charge is not in contact with coke, but may be made in open hearth, cupola or electric furnaces.

The character of the chill will depend somewhat'upon the amount of chilling to which the metal is subjected in the casting mold. When cast in a heavy chill mold, such as employed in casting the usual chilled rolls, a white iron surface or primary chill is formed, which merges gradually into a hard secondary chill somewhat softer, however, than the white iron primary chill. When cast in a lighter chill mold, such, for example, as employed in making the so-called condensed grain rolls, the chilled surface of the roll will be grayer than the rimary chill formed by casting in a heavy c '11 mold and will more closely resemble the secondary chill which is formed whenthe roll is cast in a heavy chill mold.

In all cases, however, the chill is of an unusually fine grain. It has a much greater toughness and resistance to spelling and fire cracking than that of the usual chilled iron Serial No. 136,728, filed.

Application flied latch 23, 1927. Serial No. 177,886.

rolls, and can be used in places where steel rolls have heretofore been required. The roll. nevertheless, is distinctly an iron roll, as distinguished from a high carbon steel roll or a so-called Adamite roll. The roll has the hard surface chill and the smooth close grained surface texture which are characterlstic of an iron roll and which are demanded for finishing purposes, and which give much greater wear than a high carbon steel or Adamite roll.

The metal of my roll contains cal-hon preferably somewhat higher than that of the usual hot rolls and nearer the carbon content of cold rolls. The carbon may run from, say. about 2.75 to 4 per cent. preferably about 3.00 or 3.25 to 3.75 per cent. The silicon is that of the usual ranges for iron rolls. say. about .50 to 2.50 per cent, preferaboye 75 per cent. The silicon will be varied in accordance with the usual foundry practice, depending upon the size of the casting and the character of the roll desired. In general, the higher the silicon, the softer the roll, and the lower the silicon. the harder the roll. The silicon should be sufficient so that the unchilled portions of the roll have a gray or mottled iron structure. The manganese is also that of the usual ranges of iron rolls. say, about .15 to 1.50 per cent, preferably about .20 to .50 or even .80 per cent. The phosphorus is kept much lower than usual in iron rolls and should not exceed about .20 per cent, preferably not over about .10 per cent, and for the best results should not be over about .06 per cent. The sulphur is preferably somewhat lower than the usual ranges in iron rolls. The sulphur should not exceed about .20 per cent, preferably not over about .15 per cent, and for the best results should not be over about .08 or .10 per cent. The phosphorus and sulphur are kept within the desired low limits by carefully selecting the pig iron and scrap used for the charge. The chromium may range from about .50 to 1.75 per cent, preferably from about .70 to 1.25 or even 1.50 per cent, and for best results should be about .90 to 1.25 per cent. The molybdenum may vary from about .05 to even 2.00 per cent. I have found that the best results, consistent with a minimum use of this expensive alloying metal, may be Si. 1.10; s. .041; P. .034; Mn. .36; Cr. 1.02;

A chilled roll of 16 inches diameter and 22 inches long for rolling hot strip; C. 3.52;

. Si. 1.15; S. .034; P. .060; Mn. .31; Cr. 1.15;

A chilled roll of 15 inches diameter and 20 inches long for rolling angles: C. 3.49; Si. 1.42; S. .045; P, .022; Mn. .34; Cr. 1.04; Mo. .26.

A chilled roll of 10 inches diameter and 20 inches long for rolling shapes: C. 3.38;

Si. 1.39; S. .029; P. .014; Mn. .31; Cr. 1.00;

A lighter chilled or so-called condensed grain roll of 24 inches diameter and 60 inches long for rolling rounds: C. 3.48; Si. 1.58; S. .042; P. .065; Mn. .36; Cr. 1.10; Mo. .25.

A lighter chilled or so-called condensed grain roll of 23 -inches diameter and 51 inches long for rolling beams: C. 3.41; Si. 1.29; S. .051; P. .051; Mn. .36; Cr. 1.08; M0. .264.

A lighter chilled or so-calledcondensed grain roll of 52 inches diameter and 8 4 inches long for rolling beams: C. 3.50; Si. 2.19; S. .041; P. .050; Mn. .42; Cr. .89; M0. .244. A

A lighter chilled or so-called condensed grain roll of 22 inches diameter and 62 inches long for rolling tubes: C. 3.48; Si. 1.22; S. .027; P. .050; 'Mn. .29; Cr. 1.03; Mo. .26.

\Vhile it is preferred to use a metal having the allo ing constituents set forth above, it is possib e to have present some quantities of other alloyin metals. For example, nickel may be adde to the mixture without any particular effect on the roll other than reducing the amount of clear chill unless the silicon is lowered to take care of the nickel addition. Other alloying metals may be used as tougheners or scavengers, such, for example. as vanadium.

I will now describe in greater detail the characteristics of the roll, first with particular reference to the chill formed when the roll is cast in a heavy chill mold. As is well known in the roll making art, in making a chilled roll, the wearing surface of the roll is cast against a heavy metal ring or cylinder and produces the well known chilled iron roll. The surface layer of the roll is of white iron in which the carbon is substantially all in the combined form and which is known as the primary chill. Beneath the primary chill of the usual iron roll there is a sub-structure commonly termed the mottled chill, which contains some free graphite in flake form. This sub-structure or mottled chill is of a rather coarse grain. It is hard and soft in spots, and is not suitable for a wearing surface. When turning down the usual iron roll, and especially in cutting the grooves in rolls for finishing shapes, the roll has to be discarded when the mottled chill is reached. The interior or core of the roll which is not subjected 'to the rapid cooling is of ray or mottled iron, the carbon being principally in the graphitic form.

My roll has a primary and secondary chill which are modified from and have characteristics which are distinctly difierent from and an improvement over the chills of the usual chilled iron roll. In the usual chilled iron roll there is a distinct line of demarcation between the primary and. sub-structure or mottled chills. While in the usual roll the primary chill is of clear white iron, the substructure or mot-tlechill is distinctly mottled and is characterized by the presence in a white iron matrix of distinct and fair sized flakes or hands of gra hitic carbon which are readily distinguisha Is to the naked eye.

In my chilled rolls there is no distinct line of demarcation between the primary and secondary chills, but the two chills mer e together so that it is practically impossib e to distinguish any boundary between them. The character of the iron gradually changes from the surface through the primary and secondary chills, appearing to the eye to be practically all white iron inbotll chills. Of course, in going from the surface to the core of the roll, the ercentage of combined carbon gradually ecreases and the percentage of free carbon increases, until at the inner partof the secondary chill and at the core, the metal is a gray or mottled iron. Any free carbon whlch ma be precipitated in the chilled portions 0 my roll is precipitated in the form which is or resembles temper carbon, the carbon being in the form of microscopic nodules which are practically indistinguishable to the naked eye.

The primary chill is harder than that of the primary chill of the usual chilled rolls used for hot rolling. The hardness closely approaches that of the so-called cold rolls which are chilled rolls containing especially large amounts of carbon and sulphur to ive an exceedingly hard surface for cold rolling. This hardness, however, is attained in cold rolls with a sacrifice of toughness and strength so that the iron cold rolls which which causes a rapid cooling of the metal have hertofore been made with such hardhas a much greater strength and toughness.

than the metal tinuation of the primary the usual iron what appears to in t a usual rolling mil use. The rimary chill of my rolls has a finer grain t an the primary c ill of the ordinary iron roll. It

than that of the usual iron roll. It is practically non-spalling and has a much better resistance to fire cracking than the 0111 of roll. It has a remarkable resistance to abrasion under heat and thethermalchanges to which the rolls-are sub ected in rolling hot metal. It also has a much greater resistance to shearing and crushing of the usual gray iron or chilled iron rolls, and this particularly adapts it for shape work where ton-giles or grooves are cut on the rolls. The lmprov wearing qualities are shown by the fact that my rolls are iving from two to fourtimes the tonnage 0% the ordinary clnlled rolls, before requiring redressin The texture of the roll surface, however, 18 distinctly that of an iron roll and renders the roll particularly adapted for finishing purposes, although on account of their unusual strength, the rolls may be used for intermediate rolls or even roughing rolls where a close grain wearresisting surface is desired.

I have found, particularly in the higher carbon ranges, that there is a small amount of what a pears to be temper carbon in the primary cllill. This is probably due to the rather hi her carbon content which is used and whie imparts a greater hardness than usual in the ordinary chilled iron rolls used in hot rolling. This carbon exists in the form of microscopic nodules so fine as to be individually indistinguishable to the naked eye, as contrasted with gra bits which is precipitated in the form of akes or hands.

When examined under a microscopz, the

tem-

rounded nodules of what; appears to per carbonmay. be d1stingu1shed,-but when the surface is etched as with 9.10 per cent solut-ion of nitric acid and alcohol, such carbon is completely masked and invisible, the etched structure apparently consisting of but cementite and pearlite, or in other words. white castiron. The same thing is true of be the temper carbon in the The closer grained tougher secondary chill.

of the metal allows and stronger structure the carbon to be raised to a int ahovethat usually permissible in hot to ls, and the pres ence of what appears to be temper car up 'arently concommitant with the higher n ranges. Due, however, to its fine nodular form and to th fine grain of the metal, the carbon apparently or weaken the structure of the chill, as in the case of carbon precipitated as graphite in the usual chilled or mottled cast irons.

The secondary chili is practically a conchill and has, in general, the same-type of grain structure.

nessfi have not been adapted for hot rollingiron rolls. Moreover, grooves may bOIllE' does not soften ability to form The secondary chili is of course characterlze'd by more free carbon than the primary chill, since it is not subjected to as rapid a cooling. This carbon appears to be mostly temper carbon and exists in about the same form as in the primary chill, namely, in m1- croscopic nodules which are individually practically indistinguishable to the naked eye, although the impart a slight grayish cast to the secon a? chill, particularly toward the interior 0 the rol The nodules are, however, more numerous and somewhat larger, as would be expected in going from the white iron primary chill toward the gray iron core. -The carbon in the secondary chill is distinctly diflerent from the carbon in d the sub-structure or mottled chill of the ordinary chilled iron rolls in which the carbon vexists as flakes or hands of raphite giving the characteristic mottling. lie the grain structure of the secondary chill, and particularly its portions adjacent the primary chill, closely a preaches the fineness of the prI- mary ch 1 grain structure, it is not uite as fine. However, the secondary chil grain structure is much finer than that of the usual mottled 11011 chill which forms the sub-structure of the usual primary chill. The closeness of the approach of the fineness of the grain structure of the secondary to the primary chill is shown by the fact that in cutting groovesthrough the primary chill into the seconda chill of my rolls, it is virtually impossi is to distinguish with the eve the secondary from the primary chill. Other characteristics of the secondary chill closely approach those of the primary chill, be n modified somewhat, of course, as wou d be expected by the slower rate of coolmg of the metal. The secondary chili is somewhat stron r but not quite as hard as the primary chi l. The hardness and wearmg qualit es of the secondary chill, however, sullicrentl'y closely approach those of the prime chill so that the roll may be turned down in dressing into the secondary chill without destroying its usefulness, a thing which is Impossible with the ordinary ihilled e cut in the roll through the primary and into the secondary chill. The bottoms of the grooves in the secondary chill will approximate the close grained texture and wearing qualities of the metal in the primary chill and the passes will not roughen up as is the casewhen the mottled chill is reached in the ordinary chilled roll. Therefore, while the roll may be used for plain work, it is particularly adapted for shape work due to the coves in the roll through the primary chil and into its close textured secondary chill.

I have found that the hardness of the metal in the primary chill of my chilled rolls of the preferred carton content is till lth)

about to on the Shore scleroscope scale, while the secondary chill on the same roll shows about 60 to 70. These figures show that not only is the primary chill harder than that of the usual chilled, roll for hot rolling, but the secondary chill is enormously harder than the sub-structure or mottled chill of the ordinary chilled roll.

When the metal is cast in a mold having less massive chilling rings, the chilling is of course less pronounced, so that the outer surface of the roll, instead of being practically pure white iron, is more like that of the secondary chill whichunderlies the primary chill when the roll is cast against a heavy chilling ring. Chilled rolls which are cast against the lighter chills are ordinarily known in the trade as condensed grain iron rolls. They are of course chilled rolls in that the metal is cast against a chill which results in a surface hardening, although the hardening is not carried to the full extent usual in the type of roll commonly known to the trade as a chilled roll. The term chilled cast iron rolls as used herein with reference to my rolls is intended to include the more lightly chilled or condensed grain rolls as well as the heavily chilled rolls. In the ordinary more lightly chilled or condensed grain roll, the metal in the surface 3-} lighter chill I characteristics layer is a mottled iron characterized by a rather finer mottling or grain than the more slowly cooled metal in the interior of the roll. When my roll metal is cast against a mold such as employed for making condensed grain rolls, a gram structure or mottling is produced which is much finer than that of the usual condensed grain rolls. The carbon is much more uniformly distributed and is in a much finer condition, the result being that a gray iron condensed grain roll may be produced having a much closer grain, harder surfaceandone which will roughen much less in service than that of the usual condensed grainiron roll. In general, it may be stated that the chill of a condensed grain roll made from my metal has substantially the same characteristics as those of the secondary chill, as described above. The degree to which these characteristics are present may be considerably varied by the amount of chilling to which the metal is subjected, so that the condensed grain chill may vary in the degree of its from those of that part of the' secondary chill which is next the primary chill to those of that part of the secondary chill which is next the core of a roll having a white iron primary chill.

The entire structure of my roll, including the core, as well as the chilled portions, has a much greater strength than that of the ordinary iron rolls, so that the average life of my rolls is much greater since they are praclically unbreakable under rolling mill con- ,nese about .1510 1.50

ditions in which iron rolls are used. This is of importance, because when a roll breaks the mill must be shut down and production stopped. The remarkable increased strength of my roll over the usual iron rolls is a parently due to. the eculiar action of the small amount of mo ybdenum in conjunction with the fine grain imparted to the roll by the chilling operation on a metal containing the carbon chromium, low phosphorus and low sulphur, as described herein.

While the extraordinary strong and tou h fine grained roll structure, as above escrlbed. is aggarently due to the combination of the moly enum III the metal, a somewhat similar but weaker grain structure ma apparently be produced under someconditions by chilling a high carbon chromium iron alloy havinglow' phosphorus and sulphur limits. A roll having the alloying metal and the metalloid contents as described above but without molybdenum is a weaker and inferior roll, although its appearance may a proach that of my preferred rolls. If the molybdenum be omitted, it is preferable that little, if any, nickel be present, because the presence of nickel necessitates cutting down silicon which makes the metal more diflicult to cast and control. If molybdenum is present, a small amount of nickel is not particularly objectionable, since the molybdenum apparently helps in the control of the meta If molybdenum is not present, the nickel should about .25 per cent.

While I have specifically described the preferred embodiment of my invention, it is to be understood that the invention is not limited to the herein described details, but may be otherwise embodied within the scope of the following claims.

I claim:

1. As a. new article of manufacture, a chilled cast iron roll containing total carbon about 3.00 to 3.75 per cent, chromium about 0 to 1.25 per cent, molybdenum about .15 to .50 per cent, phosphorus not over about" .06 per cent, sulphur not over about .08 r cent, silicon about .75 to 2.50 per cent, an manganese about .20 to .80 per cent, and having a close grained white iron primary chill and a secondary chill having no distinct line of demarcation between it and the primary chill and having a grain structure resembling that of the primary chill.

2. As a new article of manufacture, a chilled cast iron roll containing total carbon about 3.00 to 3.75 per cent, chromium about .70 to 1.50 per cent, molybdenum about .15 to .80 per cent, phosphorus notover .15 per cent, sulphur ,not over about .15 er cent, silicon about .50 to 2.50 per cent, an mangaper cent, and having a close grained white iron primary chill and a secon ary chill having nodistinct line of depreferably be not over 2.00 per mint, phosphorus not over cent, and having a close grained white iron prima chill and a secondary chill having no dimnct line of demarcation between it and the prima chill and having a grain structure resem ling that of the primary chill.

4. As a new article of manufacture, a chilled cast iron roll containing total carbon about 2.75 to 4.00 per cent, chromium about .50 to 1.7 5 per cent, molybdenum about .05 to about .20 per cent, and sulphur not over about .20 per cent, and having a close grained white iron primary chill and a secondary chill having no distinct line of demarcation between it and the prima] chill and having a grain structure resem ling that of the primary chill.

5. As a new article of manufacture, a chilled cast iron roll containing total carbon about 3.00 to 3.75 per cent, chromium about .70 to 1.25 per cent, molybdenum about .15 to .50 per cent, phosphorus not over about .06 per cent, sulp ur not over about .08 dper cent, silicon about .75 to 2.50 per cent, an manganese about .20 to .80 per cent.

6. As a new article of manufacture, a chilled cast iron roll containing total carbon about 3.00 to 3.75 per cent, chromium about .70 to'1.50 per cent, molybdenum about .15 to .80 per cent, hosphorus not over about .15 per cent, sulp ur not over about .15 per cent, silicon about .50 to 2.50 per cent, and manganese about .15 to 1.50 per cent.

7. As a new article of manufacture, an unannealed chilled cast iron roll containing total carbon about 2.7 5 to 4.00 per cent, chromium about .50 to 1.75 per cent, molybdenum about .15 to .80 per cent, phosphorus not over about .15 per cent, and sulphur notover about .15 per cent, together with sufiicient silicon to produce a gray or mottled iron slllilllctllle in the unchilled portions of the ro a 8. As anew article of manufacture, an unannealed chilled cast iron roll containing total carbon about 2.75 to 4.00 per cent chromium about .50 to 1.75 per cent, molyb enum about .05 to 2.00 per cent, phosphorus not over about .20 per cent', and sulphur not over about .20 per cent, together with. sufiicient silicon to produce a ray or mottled iron stiillicture in the unchilled portionsof the ro 9. As a new article'of manufacture, a chilled cast iron roll containing total carbon about 3.00 to 3.75 per cent, chromium about .70 to 1.25 per cent, phosphorus not over about .10 per cent, sulphur not over about .10 per cent, silicon about .50 to 2.50 per cent manganese about .15 to 1.50 per cent, and nickel not over about .25 er cent, and having a close grained white iron primary chill and a secon ary chill having no distinct line of demarcation between it and the primarychill and having a grain structure resembling that of the primary chill and a gray or nlilofizled iron core underlying the secondaryc 1 a a 10. As anew article of manufacture, a chilled cast iron roll containing total carbon about 3.00 to 3.75 per cent, chromium about .7 0 to 1.25 per cent, phosphorus not over about .10 per cent, sulphur not over about .10(per cent, silicon about .50 to 2.50 per cent, an manganese about .15 to 1.50 per cent, and having a close grained white iron primary chill an a secondary chill having no-distinct line of demarcation between it and the primary chill and having a grain structure resembling that of the primary chill and a gra or mottled iron core underlying the secon ary chill.

In testimony whereof I have hereunto set my hand.

HARRY E. WALTERS.

- chill.

marcation between it and the primary chill and having a grain structure resembling that of the primary chill.

3. As a new article of manufacture, a chilled cast iron roll containing total carbon about 2.75 to 4.00 per cent, chromium about .50 to 1.75 per cent, molybdenum about .05 to 2.00 per cent, phosphorus not over about .15 per cent and sulphur not over about .15 per cent, and having a close grained white iron prima chill and a secondary chill having no distinct line of demarcation between it and the primer chill and having a grain structure resem ling that of the primary 4. As a new article of manufacture, a chilled cast iron roll containing total carbon about 2.75 to 4.00 per cent, chromium about .50 to 1.75 per cent, molybdenum about .05 to 2.00 per cent, phosphorus not over about .20

about 3.00 to 3.75 per cent, chromium about,

.70 to 1.25 per cent, molybdenum about .15 to .50 per cent, hosphorus not over about .06 per cent, sulp ur not over about .08 er cent, silicon about .75 to 2.50 per cent, an manganese about .20 to .80 er cent.

6. As a new article of manufacture, a chilled cast iron roll containing total carbon about 3.00 to 3.75 per cent, chromium about .70 to 1.50 per cent, molybdenum about .15 to .80 per cent, hosphorus not over about .15 per cent, sulp ur not over about .15 per cent, silicon about .50 to 2.50 per cent, and manganese about .15 to 1.50 per cent.

7. As a new article of manufacture, an unannealed chilled cast iron roll containing total carbon about 2.75 to 4.00 per cent, chromium about .50 to 1.75 per cent, molybdenum about .15 to .80 per cent, phosphorus not over A Patent 'No. 1,627,626.

prefer read preferably;

about .15 per cent, and sulphur not over about .15 per cent, together with suflicient silicon to produce a gray or mottled iron stlillicture in the unchilled portions of the ro 8. As a new article of manufacture, an unannealed chilled cast iron roll containing total carbon about 2.75 to 4.00 per cent chromium about .50 to 1.75 per cent, molyb enum about .05 to 2.00 per cent, phosphorus not over about .20 per cent, and sulphur not over about .20 per cent, together with sufficient silicon to produce a ray or mottled iron stlilllcture in the unchll led portions of the ro 9. As a new articleof manufacture, a chilled cast iron roll containing total carbon about 3.00 to 3.75 per cent, chromium about .70 to 1.25 per cent, phosphorus not over about .10 per cent, sulphur not over about .10 per cent, silicon about .50 to 2.50 per cent, manganese about .15 to 1.50 per cent, and nickel not over about .25 per cent, and having a close ained white iron primary chill and a secon ary chill having no distinct line of demarcation between it and the primary chill and having a grain structure resembling that of the primary chill and a gray or nliloizfled iron core underlying the secondary c 1 10. As a new article of manufacture, a chilled cast iron roll containing total carbon about 3.00 to 3.75 per cent, chromium about .70 to 1.25 per cent, phosphorus not over about .10 per cent, sulphur not over about .10 er cent, silicon about .50 to 2.50 per cent, an manganese about .15 to 1.50 per cent, and having a close grained white iron primary chill and a secondary chill having no distinct line of demarcation between it and the primary chill and having a grain structure resembling that of the primary chill and a gra or mottled iron core underlying the secon ary chill.

In testimony whereof I have hereunto set my hand.

HARRY E. WALTERS.

Granted May 10, 1927, to

HARRY E. \VALTERS.

It hereby certified that error appeals numbered patent requiring correction as in the printed specification of the above- -follows: Page 1, line 72, for the word page 3, line 130, for the word carton read carbon;

and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealedthis 7th day of June, A. I). 1927.

M. J. MOORE, Acting Commissioner of Patents.

Ill]

Certificate of Correction.

Patent No. 1,627,626. Granted May 10, 1927, to

HARRY E. WALTERS.

It hereby certified that error appeals in the printed specification of the abovenumbered patent requiring correction as follows: Page 1, line 72, for the word refer read re enabl a e 3, line 131) for the word carton read carbon;

P P 2/; P k, a

and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent ()fiiee.

Signed and sealed this 7th day of June, A. D. 1927.

M. J. MOORE,

Acting (l'o'nwmlssz'omr of Patents. 

